This appears to be caused by soil/water that is too alkaline or salty. Salt burn on plants usually appears on the tip and/or margins of the leaves. You can improve the soil by flooding (leaching) the salt down out of the root zone. Regular deep watering is an ideal way to prevent this. For example if you have automated irrigation it’s best to set it for less days, but more minutes. Instead of frequently, but for only a few minutes, which would allow salts to accumulate at the roots of the plant. Alkaline soil is best treated with a soil acidifier, available from your local nursery or the addition of wood chip mulch or compost. A soil pH test would be informative. You should be able to find a simple test at your local garden center or on-line.